1. Field of the Invention
The present disclosure relates to an output current distortion compensating apparatus in an inverter, and more particularly to an output current distortion compensating apparatus in an inverter configured to prevent an output current distortion in an inverter by generating an additional compensation voltage to cope with a distortion phenomenon of an output current caused by an error in a dead time compensation voltage.
2. Description of Related Art
An inverter for motor driving can be used for various purposes. Examples of the inverter for driving a motor may include industrial manufacturing facilities, building air conditioners and elevators. A conventional 3-phase inverter receives an electric power of 3-phase (R, S, T) to output a 3-phase output of U, V, and W phases to a motor, where, two switching elements (divided to a +phase switching element and a +phase switching element based on current polarity) such as IGBTs (insulated gate bipolar transistors) are formed at each phase in order to control speed and current in the motor, and a desired current or voltage is outputted by turning on or off a relevant switching element in response to an inputted PWM (Pulse Width Modulation) control signal.
At this time, if a +phase switching element and a −phase switching element on the same phase are turned on, a current more than a threshold current exceeding a rated current of the switching element flows to break the switching elements, and in order to protect the switching elements against the breakage, a dead time is inserted to the PWM control signal controlling the switching element to protect the switching elements.
However, there is a disadvantage in the conventional method in that an actual dead time voltage is changed by ON/OFF characteristics of a power switch element, and a dead time compensation voltage generates an error responsive to noises detected by a current detector, where the error in turn generates a distortion to a voltage applied to an electric motor, leading to occurrence of hunting phenomenon in which current is greatly fluctuated.